3RW3 semiconductor motor control unit
SIRIUS System Manual
GWA 4NEB 430 0999-02b
8-31
Changing settings
The potentiometer settings are scanned before each switching operation
("ON" or "OFF").
If, for example, the setting of the potentiometer for starting time is changed
while the motor is running up, the change does not come into effect until
the next start.
Starting voltage
The starting voltage should be set to a value at which the motor starts rap-
idly.
Ramp time
The ramp time should be set such that the motor can run up within the time
defined in this way.
If the star time for star-delta starting is known, the ramp time can be set to
this value.
Coasting-down time
The potentiometer for the coasting-down time is for setting the duration of
the voltage ramp for coasting down. This parameter can be used to make
the motor run-down longer than it would be if the motor were merely to
coast to a stop.
The motor coasts to a stop on its own if this potentiometer is set to a value
of 0.
Switching frequency
To prevent thermal overloading of the devices, the maximum permissible
switching frequency must be adhered to and the correction factor tables
must be used (see the installation guidelines in Section 8.3.2).
Starting time
In order to obtain optimum operating conditions for the 3RW3 soft starter,
the setting for the starting time should be approx. 1 second longer than the
resultant motor run-up time, in order to ensure that the internal jumpering
contacts do not have to carry the starting current. This protects the internal
jumpering contacts and increases their service life. Longer starting times
increase the thermal load on the devices and the motor unnecessarily and
lead to a reduction in the permissible switching frequency.
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